(原) 2.1 Zookeeper原生API使用

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Zookeeper原生API使用

1、jar包引入，演示版本为3.4.6，非maven项目，可以下载jar包导入到项目中

<dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.6</version>
</dependency>

2、创建zookeeper连接

　　ZooKeeper(java.lang.String connectString, int sessionTimeout, org.apache.zookeeper.Watcher watcher)

- connectString：zookeeper服务地址，例如“192.168.117.128:2181”
- sessionTimeout ：超时时间，单位为毫秒
- watcher：实现org.apache.zookeeper.Watcher接口的实现类，需实现process(WatchedEvent watchedEvent) 方法

　　ZooKeeper zooKeeper = new ZooKeeper("192.168.117.128:2181",5000, new MyWatcher());

示例代码：

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import java.io.IOException;

/**
 *
 * zookeeper连接
 */
public class CreateSession implements Watcher{
    private static ZooKeeper zooKeeper;

    @Override
    public void process(WatchedEvent watchedEvent) {

        if(watchedEvent.getState().equals(Event.KeeperState.SyncConnected)) {
            doBus();
        }
        System.out.println("接收内容："+watchedEvent.toString());
    }

    private void doBus() {
        System.out.println("做业务！");
    }

    public static void main(String[] args) {
        try {
            zooKeeper = new ZooKeeper("192.168.117.128:2181",5000, new CreateSession());
            System.out.println(zooKeeper.getState());
            Thread.sleep(5000);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

　　ps:此处没有新创建新的java类实现Watcher,而是直接在本类中实现Watcher接口并重写process方法

3、同步创建

　　create(java.lang.String path, byte[] data, java.util.List<org.apache.zookeeper.data.ACL> acl, org.apache.zookeeper.CreateMode createMode)

- path：创建节点路径，需保证父节点已存在
- data：节点数据
- acl:权限列表
  - 提供默认的权限OPEN_ACL_UNSAFE、CREATOR_ALL_ACL、READ_ACL_UNSAFE
    - OPEN_ACL_UNSAFE：完全开放
    - CREATOR_ALL_ACL：创建该znode的连接拥有所有权限
    - READ_ACL_UNSAFE：所有的客户端都可读
  - 自定义权限　　
```
ACL aclIp = new ACL(ZooDefs.Perms.READ,new Id("ip","127.0.0.1"));
                ACL aclDigest = new ACL(ZooDefs.Perms.READ| ZooDefs.Perms.WRITE,
                        new Id("digest", DigestAuthenticationProvider.generateDigest("id:pass")));
```
  - session设置权限　
```
zk.addAuthInfo("digest", "id:pass".getBytes());　　
```
- createMode:节点类型
  - PERSISTENT：持久化节点
  - PERSISTENT_SEQUENTIAL：持久化有序节点
  - EPHEMERAL：临时节点（连接断开自动删除）
  - EPHEMERAL_SEQUENTIAL：临时有序节点（连接断开自动删除）

示例代码：　　

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.ACL;
import org.apache.zookeeper.data.Id;
import org.apache.zookeeper.server.auth.DigestAuthenticationProvider;

import java.io.IOException;
import java.security.NoSuchAlgorithmException;

/**
 * 创建节点(同步)
 * Created by scot on 2016/6/8.
 */
public class CreateSessionSync implements Watcher{
    private static ZooKeeper zooKeeper;

    @Override
    public void process(WatchedEvent watchedEvent) {

        if(watchedEvent.getState().equals(Event.KeeperState.SyncConnected)) {
            doBus();
        }
        System.out.println("接收内容："+watchedEvent.toString());
    }

    private void doBus() {
        try {
            if(null != zooKeeper.exists("/note_scot/note_scot_a",false)) {
                System.out.println("/note_scot/note_scot_a 节点已存在");
                return;
            }
            String path = zooKeeper.create("/note_scot/note_scot_a","aa".getBytes(),
                    ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);


           /*权限相关
            try {
                ACL aclIp = new ACL(ZooDefs.Perms.READ,new Id("ip","127.0.0.1"));
                ACL aclDigest = new ACL(ZooDefs.Perms.READ| ZooDefs.Perms.WRITE,
                        new Id("digest", DigestAuthenticationProvider.generateDigest("id:pass")));
                zooKeeper.addAuthInfo("digest", "id:pass".getBytes());　
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
            }*/

            System.out.println("zookeeper return:" + path);
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        try {
            zooKeeper = new ZooKeeper("192.168.117.128:2181",5000, new CreateSessionSync());
            System.out.println(zooKeeper.getState());
            Thread.sleep(5000);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

4、异步创建

　　create(java.lang.String path, byte[] data, java.util.List<org.apache.zookeeper.data.ACL> acl,

　　　　　 org.apache.zookeeper.CreateMode createMode, org.apache.zookeeper.AsyncCallback.StringCallback cb, java.lang.Object ctx)

- StringCallback cb：回调接口，执行创建操作后，结果以及数据发送到此接口的实现类中
- Object ctx：自定义回调数据，在回调实现类可以获取此数据

示例代码：

import org.apache.zookeeper.*;

import java.io.IOException;

/**
 * 创建节点(异步)
 * Created by scot on 2016/6/8.
 */
public class CreateSessionASync implements Watcher{
    private static ZooKeeper zooKeeper;

    @Override
    public void process(WatchedEvent watchedEvent) {

        if(watchedEvent.getState().equals(Event.KeeperState.SyncConnected)) {
            doBus();
        }
        System.out.println("接收内容："+watchedEvent.toString());
    }

    private void doBus() {
            zooKeeper.create("/note_scot/note_scot_b","aa".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,
                    CreateMode.PERSISTENT_SEQUENTIAL,new IStringCallBack(),"testAsync");
    }

    public static void main(String[] args) {
        try {
            zooKeeper = new ZooKeeper("192.168.117.128:2181",5000, new CreateSessionASync());
            System.out.println(zooKeeper.getState());
            Thread.sleep(5000);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    static class IStringCallBack implements AsyncCallback.StringCallback {

        @Override
        public void processResult(int i, String s, Object o, String s2) {
            System.out.println("i="+i);//创建成功返回0
            System.out.println("s="+s);//自定义节点名称
            System.out.println("o="+o);//自定义回调数据
            System.out.println("s2="+s2);//最终节点名称（顺序节点最终名称与自定义名称不同）

        }
    }
}

常用方法列表：

String create(final String path, byte data[], List acl, CreateMode createMode)	参数：路径、 znode内容，ACL(访问控制列表)、 znode创建类型；用途：创建znode节点
void delete(final String path, int version)	参数：路径、版本号；如果版本号与znode的版本号不一致，将无法删除，是一种乐观加锁机制；如果将版本号设置为-1，不会去检测版本，直接删除；用途：删除节点
Stat exists(final String path, Watcher watcher)	参数：路径、Watcher(监视器)；当这个znode节点被改变时，将会触发当前Watcher 用途：判断znode节点是否存在
Stat exists(String path, boolean watch)	参数：路径、并设置是否监控这个目录节点，这里的 watcher 是在创建 ZooKeeper 实例时指定的 watcher；判断znode节点是否存在
Stat setData(final String path, byte data[], int version)	参数：路径、数据、版本号；如果为-1，跳过版本检查用途：设置znode上的数据
byte[] getData(final String path, Watcher watcher, Stat stat)	参数：路径、监视器、数据版本等信息用途：获取znode上的数据
List getChildren(final String path, Watcher watcher)	参数：路径、监视器;该方法有多个重载用途：获取节点下的所有子节点

下一节：2.2ZkClient使用

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原文地址：https://www.cnblogs.com/shengkejava/p/5611671.html